Kexin is a prohormone processing protease found in the budding yeast (S. cerevisiae) that shares structural similarities with the bacterial protease subtilisin. It is encoded by the yeast gene KEX2 and usually referred to in the scientific community as Kex2p. The first mammalian homologue of this protein to be identified was furin. This enzyme catalyses the following chemical reaction Cleavage of -Lys-Arg- and -Arg-Arg- bonds to process yeast alpha-factor pheromone and killer toxin precursors.